1. Field of the Invention
The present invention is directed to the synthesis of the hydrochloride salt of certain selected catecholamine derivatives. More particularly, the present invention is directed to the use of cesium chloride (CsCl) as the chloride ion donor in the final step for obtaining the hydrochloride salt of the aforementioned compounds.
2. Description of the Prior Art
U.S. Pats. Nos. 3,809,714, 3,825,583, 3,868,461 and pending U.S. patent applications Ser. No. 548,606, filed Feb. 10, 1975 (officially allowed), and Ser. No. 578,079, filed May 16, 1975, all disclose compounds which fall within the above-described generic formula.
A review of these materials will readily show that conventionally, the chloride salt form (which is usually preferred because of its extremely favorable pharmaceutical acceptability) is obtained by first preparing the free base form corresponding to the above generic formula and then treating the free base so obtained with a stoichiometric amount of hydrochloric acid. However, due to the unstable nature of the free base of the above-described compounds, this procedure is quite undesirable as it leads to (1) discoloration, but more importantly, (2) excessive loss of yield and purity of the final product. This is especially true when batch sizes are substantially increased for commercial production.
Accordingly, a need exists for a novel means to prepare the hydrochloride salt of the aforementioned described compounds such that (1) discoloration and (2) excessive loss of yield and purity are minimized.